TROPICAL CYCLONE FORMATION: MONITORING W. ATLANTIC
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(T. F. “Storm” Walsh III)
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CURRENT 2016 ATLANTIC TROPICAL CYCLONE TOTALS:
TOTAL STORMS: 5
INTENSE HURRICANES: 0
StormW’s Seasonal Hurricane Forecast:
TOTAL STORMS: 14-16
INTENSE HURRICANES: 3-4
Good evening everyone!
The weak area of low pressure that was being monitored in the extreme NE GOMEX, has moved inland over the NE Florida peninsula. Albeit decent convection is noted just offshore the Big Bend area, the actual low can be seen spinning over the peninsula in RGB satellite loop imagery. Thus ends the probability of a Tropical Depression developing.
Based on current steering and satellite loop imagery, steering has currently collapsed, and the low appears to be stationary at the moment. The WPC QPF forecasts still call for very excessive rainfall totals over the next 5-7 days over portions of W. GA., central and south AL., and SE MS. I’ll explain…the system had been moving to the NE, before stalling. Based on my analysis of current forecast steering maps, the low center may remain quasi-stationary for the next 18-24 hours. It appears WPC is basing the projected QPF amounts over the mentioned areas, as we are currently thinking the entire system may perform a cyclonic loop, which would bring rainfall over the mentioned areas.
WPC QPF FORECAST 5 AND 7 DAYS
Residents over those areas and surrounding areas should monitor local NWS statements and advisories regarding the potential for heavy rainfall and possible flash flooding at some locations as steering patterns have shown to change in as little as a 24 hour period.
The NWS Warning and Advisory map is interactive. Just click on your area of interest for the latest statements and warnings.
Elsewhere, I am still monitoring the area of disturbed weather in the WATL, located NE of the southern Bahamas area. While this hasn’t shown any organization at the surface, convection over the past 2 hours has become better organized and a bit more consolidated. Vorticity at the moment is confined to the mid levels of the atmosphere. The NHC has designated only a LOW (20%) probability of cyclone formation. Based on my analysis of the current wind shear forecast, and water vapor satellite loop imagery, as the upper level low to the west of this disturbance backs away, upper level winds are forecast to become fairly conducive during the next 24-30 hours, before returning to unfavorable for development. While I concur with the NHC probability, I do believe this has that small window of opportunity to become a little better organized, and maybe try to develop a good surface reflection, prior to wind shear increasing.
Based on satellite loop analysis and current steering, this disturbance is moving to the NNW, and given its positioning in relation to the ridge, should begin to move more toward the north in about 18 hours, and then eventually off to the NE.
Elsewhere, another Tropical Wave is getting ready to exit the African continent. Convection has diminished greatly over the past 6 hours, however I will be keeping tabs on this, as it appears there is another break in the SAL / African dust situation. The current TPW animation suggests a surge of TPW / Moisture in which this wave may be able to work with. I will continue to monitor this wave for any significant changes once it gets into the Atlantic.
Yesterday evening, I mentioned in one of the weather chats I belong to, I would touch on the SAL situation we’ve seen most of the season. Typically, July has the most numerous and most severe SAL outbreaks. It would almost seem this season, that an extended period of dust outbreaks has occurred. Typically, dust rolls out into the Atlantic on average every 3-5 days. It appears this season, one of the culprits for all of the dust we’ve seen thus far, seems to have been what I feel has been an abnormally stronger Azores Bermuda high, which through June and July, had been parked further south and east, closer to Africa. This not only produced subsidence, causing a lack of instability, but aided in getting vast amounts of dust into the MDR. However, you could consider the main factor to be, the lack of any significant rainfall over the NW Sahel region (shown in the graphics). I’ve provided current 10 day total rainfall forecast maps. You can see where the greatest rainfall amounts are projected. This is just south of the Sahel area. The Sahel region, and northward, is where the African dust originates. The heavier rainfall amounts have been further south, due to the fact the Gulf of Guinea SST’ anomalies show the Gulf of Guinea anomalies to be warmer than average. What we need to see, is for the Gulf of Guinea to become cooler, which through the resultant temperature and pressure gradients, allows for the ITCZ or Monsoon Trough to be lifted further north, into the NW Sahel, allowing for more rainfall over that region. This would aid in cutting down the African dust regime.
AFRICA SATELLITE IMAGERY (DUST CHANNEL…DUST IS PINK/MAGENTA COLORS)…CLICK IMAGE FOR CLOSE UP IMAGE
The ECMWF, GFS, and to some extent, the CMC GGEM tend to indicate lowering 500 mb pressure anomalies near the Cape Verde islands in about 5-6 days.
Now, modeling from NASA still indicates we will continue to see dust in the Atlantic, but with breaks in between at various periods. I read a good paper from the AMS online journal, authored by Scott A. Braun, with the suggestions that the SAL may not always kill tropical cyclone genesis. However, as we’ve noticed (and through my 15 years of tropical cyclone forecasting), it seems almost 99% of the time, a tropical system will succumb to the SAL.
NASA DUST PROJECTION 7 DAYS
NASA DUST PROJECTION 10 DAYS
AMS JOURNAL PAPER ON RE-EVALUATING THE ROLE OF THE SAL
Now, albeit the NASA modeling indicates more dust incidents, it does indicate a decent surge of TPW during days 6-10. If you remember, we followed the TPW surge across the Atlantic a few days to one week ago, which led to the development of Earl, and is aiding the disturbed weather east of the Bahamas. So, all may not be lost this season. Again, as I’ve stated a couple of times previously, I’m not looking for much as far as a Cape Verde season, although we could see development in that area later in the season. In the big picture, looks like we’ll have to rely on tropical waves to slide under the “radar” so to speak (i.e. Earl; current disturbance) for more of close in development type situations.
Elsewhere, Tropical Storm formation is not expected during the next 5-7 days
T. F. “STORM” WALSH III
GMCS, USCG (ret)
METEOROLOGIST / HURRICANE SPECIALIST /SEVERE WEATHER SPECIALIST
MEMBER WEST CENTRAL FLORIDA AMS